There is known a thread-cutting tap in which a thread is circumferentially divided by a spiral or straight flute into divided portions, and a cutting edge is defined by cooperation of ends of the respective divided portions, namely, defined by end faces of the respective divided portions and extends along the spiral or straight flute, wherein the thread has a thread profile that becomes from an incomplete profile with its crest portion being cut, to a complete profile, in a direction away from a distal end of a chamfered portion of the thread-cutting tap toward a complete thread portion of the thread-cutting tap. There are proposed a plurality of taps in which each of the cutting edges is chamfered to restrain chipping (small breakage caused on the cutting edge) which could be caused in the known thread-cutting tap during the cutting operation. For example, in Patent Document 1, there is disclosed a technique of chamfer a part of a rake face which is contiguous to the cutting edge, wherein the chamfered part extends circumferentially rearwardly as it extends toward a crest of the thread. Further, in Patent Document 2, there is disclosed a technique of chamfering a part of a rake face which is contagious to the cutting edge, such that the chamfered part provides a negative rake. Moreover, there is proposed a technique of rounding a part of a rake face which is contagious to the cutting edge.